var year = prompt("请输入年份: ");
var month = prompt("请输入月份: ");
year = Number(year);
month = Number(month);

//1980年有多少天？
//365 366

 function runNian() {
    if (year % 400 === 0 || (year % 4 === 0 && year % 100 !== 0)){
        return true;
    } else {
        return false;
    }
}

var days = 0;
//1980年全年 +到 2018年全年
for (var i = 1980; i < year; i++){
    if (runNian(i)){
        days += 366;
    }else {
        days += 365;
    }
}

//1月 - 4月全月一共有多少天

for (var k = 1; k < month; k++){
    switch (k){
        case 1:
            days += 31;
            break;
        case 2:
            if (runNian(year)){
                days += 29;
            }else {
                days += 28;
            }
            break;
        case 3:
            days += 31;
            break;
        case 4:
            days += 30;
            break;
        case 5:
            days += 31;
            break;
        case 6:
            days += 30;
            break;
        case 7:
            days += 31;
            break;
        case 8:
            days += 31;
            break;
        case 9:
            days += 30;
            break;
        case 10:
            days += 31;
            break;
        case 11:
            days += 30;
            break;
        case 12:
            days += 31;
            break;
    }
}


//因为1980年的1月1日前面有两个空位所以加2
days += 2;

console.log(days);


//算出起始位置
var start = days % 7;
console.log(start);

//选上这个标签
var day = document.querySelector("#day");

//上一个月一共有多少天?
var prevDay = 0;
//找到上一个月多少天

switch (month - 1){
    case 1:
        prevDay += 31;
        break;
    case 2:
        if (runNian(year)){
            prevDay += 29;
        }else {
            prevDay += 28;
        }
        break;
    case 3:
        prevDay += 31;
        break;
    case 4:
        prevDay += 30;
        break;
    case 5:
        prevDay += 31;
        break;
    case 6:
        prevDay += 30;
        break;
    case 7:
        prevDay += 31;
        break;
    case 8:
        prevDay += 31;
        break;
    case 9:
        prevDay += 30;
        break;
    case 10:
        prevDay += 31;
        break;
    case 11:
        prevDay += 30;
        break;
    case 12:
        prevDay += 31;
        break;
}



//本月一共有多少天？
var thisDay = 0;
//找到上一个月多少天
switch (month){
    case 1:
        thisDay += 31;
        break;
    case 2:
        if (runNian(year)){
            thisDay += 29;
        }else {
            thisDay += 28;
        }
        break;
    case 3:
        thisDay += 31;
        break;
    case 4:
        thisDay += 30;
        break;
    case 5:
        thisDay += 31;
        break;
    case 6:
        thisDay += 30;
        break;
    case 7:
        thisDay += 31;
        break;
    case 8:
        thisDay += 31;
        break;
    case 9:
        thisDay += 30;
        break;
    case 10:
        thisDay += 31;
        break;
    case 11:
        thisDay += 30;
        break;
    case 12:
        thisDay += 31;
        break;
}

for (var j =prevDay - start + 1; j <= prevDay;j++){
    day.innerHTML += '<span class="h">' + j + '</span>';
}

//取到今天
var d = new Date().getDate();

for (var s = 1; s <= thisDay; s++){
    if (s == d){
        day.innerHTML +='<span class="today">' + s + '</span>';
    }else{
        day.innerHTML +='<span>' + s + '</span>';
    }
}

//总空出位是42位
var num = 42;

//算出还剩几个位置
var endDay = num - start - thisDay;

for (var e = 1; e<=endDay;e++){
    day.innerHTML += '<span class="h">' + e + '</span>';
}


//赋值标题的年和月

document.querySelector("#nian").innerHTML = year;

document.querySelector("#yue").innerHTML = month;